1. Field of the Invention
The present invention relates to an electric motor, particularly to an electric motor which has an armature providing magnetic poles disposed with mutually facing magnetic poles being different from each other in their magnetic polarities energized by one coil.
2. Description of the Related Art
Conventionally, there have been in consideration various types of electric motors having different structures. However, each of the conventional electric motors is formed in a manner such that each of its poles has one or more than one winding coils.
In making a conventional electric motor, since one or more than one coils are wound around each pole, not only it is difficult to reduce a production cost, but also it is difficult to manufacture an electric motor having a relatively small pole pitch. Moreover, with regard to the structure of a linear motor, since there is a relatively large amount of magnetic flux leaking between an armature and a secondary, the motor""s thrust with respect to an exiting current is thus comparatively small, resulting in a low motor efficiency. In addition, since an attraction force of magnetism acts only in one direction between the armature and the secondary, there is a relatively large load on a support structure of the secondary. As a result, a distortion in the motor structure and some other disadvantages, thus making it difficult to put the motor into practical use.
Accordingly, it is an object of the present invention to provide an improved electric motor capable of easily realizing a multiple polarization with the use of only one coil even if a pole pitch is small. Further, if an electric motor is a linear motor, such a linear motor is so formed that it is possible to reduce the leakage of magnetic flux passing between an armature and a secondary, thereby reducing an undesired magnetic attraction between the armature and the secondary.
One of the features of the present invention is that it is an electric motor which comprises an armature having a core formed by a magnetic material and having a coil wound around the core, and a secondary disposed with a clearance to the armature and supported to be relatively movable with respect to the armature. Specifically, the core has a plurality of pairs of mutually facing magnetic poles which are formed in a manner such that the secondary is allowed to be disposed between each pair of the magnetic poles, the plurality of magnetic poles are arranged in a direction in which the secondary is relatively movable with respect to the armature, every two mutually neighbouring magnetic poles arranged in the relatively movable direction on the secondary side are set to have mutually different magnetic polarities.
Namely, each pair of the magnetic poles are different in their magnetic polarities, a plurality of magnetic poles are arranged in a manner such that a flat plate like secondary or a circular cylindrical secondary may be interposed between each pair of magnetic poles, along a direction in which the secondary is relatively movable with respect to the armature. At this time, a plurality of pairs of magnetic poles arranged on the same one side of the secondary are alternatively different in their magnetic polarities along a direction in which the secondary is relatively movable with respect to the armature. For example, a plurality of pairs of the magnetic poles are extending from the base portions of the core. Among them, when a first polarity (for example, N pole) side of one pair of magnetic poles is disposed above the secondary, while a second polarity (for example, S pole) side thereof is disposed beneath the secondary, a second polarity (S pole) side of an adjacent pair of magnetic poles is disposed above the secondary, while a first polarity (N pole) side thereof is disposed beneath the secondary. In this way, when an exciting current is caused to flow through the coil wound around armature in accordance with a predetermined circuit, a plurality of alternatively arranged magnetic fields will be formed along a plurality of pairs of magnetic poles. At this time, the alternatively arranged magnetic fields will enable the secondary to have a relative movement.
In other words, it is also possible that an electric motor of the present invention comprises an armature and a relatively movable secondary. Such an electric motor may be further composed providing one side magnetic pole teeth magnetically coupled to one side magnetic pole of the armature and arranged respectively in a first stage (for example, an upper stage) and in a second stage (for example, a lower stage) disposed in a direction substantially perpendicular to the moving direction of the secondary, and the other side magnetic pole teeth magnetically coupled to the other one side magnetic pole of the armature and arranged respectively in a first stage (for example, an upper stage) and in a second stage (for example, a lower stage) disposed in a direction substantially perpendicular to the moving direction of the secondary. The magnetic pole teeth of the first stage provided on one side and the magnetic pole teeth of the first stage provided on the other side may be arranged alternatively with respect to the moving direction of the secondary. Meanwhile, the magnetic pole teeth of the second stage provided on one side and the magnetic pole teeth of the second stage provided on the other side may be arranged alternatively with respect to the moving direction of the secondary. In this way, the secondary may be disposed between the plurality of magnetic pole teeth of the first stage (provided on both one and the other sides), and the plurality of magnetic pole teeth of the second stage (provided on both one and the other sides).